In an inserting machine for mass mailing, there is a gathering section where enclosure material is gathered before it is inserted into an envelope. This gathering section is sometimes referred to as a chassis subsystem, which includes a gathering transport with pusher fingers rigidly attached to a conveyor belt and a plurality of enclosure feeders mounted above the transport. If the enclosure material contains many documents, these documents must be separately fed from different enclosure feeders. After all the released documents are gathered, they are put into a stack to be inserted into an envelope in an inserting station. Envelopes are separately fed to the inserting station, one at a time, and each envelope is placed on a platform facing down with its flap flipped back all the way. At the same time, mechanical fingers or a vacuum suction device are used to hold the front face of the envelope on the platform while the throat portion of the back face of the envelope is pulled upward to open the envelope. The stack of enclosure material is than automatically inserted into the opened envelope.
In the past, vacuum suction has been used to open envelopes as a precursor to material insertion. For example, U.S. Pat. No. 5,052,168 (DeWitt el al.) discloses a method and an apparatus to spread open an envelope where two suction cups are placed on the opposing faces of the envelope. An air flow is drawn through two respective suction arms to produce a negative air pressure to allow the suction cups to seal with the respective faces of the envelope. The suction cups are then moved away from each other in order to spread open the envelope. A vacuum pump, along with a plurality of bleed valves, release valves and dump valves, is used to produce the necessary suction force. In the method disclosed by DeWitt et al, only one suction cup is used to pick up the throat of the envelope. In general, it is preferred that a number of suction cups be positioned around the throat section of the envelope in order to spread open the envelope. The number of suction cups used is usually determined by the width of the envelope. As shown in FIG. 1, an envelope 100 has a flap 102 and a throat portion 104. After the flap 102 is flipped out as illustrated, four section cups are evenly spaced around the throat portion 104 at four pickup points A, B, C and D to open the envelope 100.
Like other similar designs, the method disclosed by DeWitt et al. uses a constantly running vacuum pump to draw the air flow in order to open and maintain the opening position of envelopes for either material insertion or extraction. The various valves in the vacuum manifold are opened or closed whenever vacuum is required for the suction cups to pick up the faces of the envelope. Typically, a large A.C. vacuum pump is required to produce the necessary suction force. The disadvantages of using such a vacuum pump in an inserting machine include:
1) energy is wasted because the power consumption of a large pump is high;
2) energy is wasted because the pump is kept running even when it is not used to open an envelope; and
3) the noise levels generated by the constantly running pump are high.
It is advantageous to provide a method and a device for opening envelopes in an inserter station wherein the vacuum or low air pressure needed for suction is produced intermittently for a short period of time and, after the throat is opened, the envelope opening position can be mechanically maintained as long as it is required without relying on the suction force within the suction cup.